title: Biotransformation of mogrosides from Siraitia grosvenorii Swingle by Saccharomyces cerevisiae.
abstract: Mogrosides are a group of triterpenoidal saponins from the fruit of Siraitia grosvenorii Swingle; they are intensely sweet and have consequently been used as a substitute for sugar by the food industry. The lack of efficient methods to produce specific mogrosides has hindered investigation of the relationship between their structure and bioactivity, e.g., down-regulation of blood glucose levels, anti-inflammation, and antiviral infection. Here, we attempt to selectively convert the major saponin mogroside V, a mogrol pentaglucoside, into mogroside III E, a triglucoside, via the β-glucosidases of the budding yeast Saccharomyces cerevisiae. We report that the β-glucopyranosyl and β-glucopyranosyl-(1→2)-β-d-glucopyranosyl attached on C-3 and -24 of mogrol, respectively, were resistant to hydrolysis by yeast β-d-glucosidases. We further screened 16 mutants bearing single defective glucanase or glucosidase genes, thereby demonstrating that Exg1 is a major enzyme of the initiation of mogroside V conversion. Deletion of the KRE6 gene unexpectedly facilitated the production of mogroside III E in yeast culture. This paper demonstrates that yeast knockout mutants are a valuable tool for saponin modification and for studying the specificity of glucosidase function.
authors.affiliation: Institute of Food Science and Technology, National Taiwan University , 59, Lane 144, KeeLung Road, Sec. 4 Taipei 106, Taiwan, ROC.
authors.forename: Chun-Hui
authors.initials: CH
authors.lastname: Chiu
authors.forename: Reuben
authors.initials: R
authors.lastname: Wang
authors.forename: Cho-Ching
authors.initials: CC
authors.lastname: Lee
authors.forename: Yi-Chen
authors.initials: YC
authors.lastname: Lo
authors.forename: Ting-Jang
authors.initials: TJ
authors.lastname: Lu
mesh_terms: D001709:Biotechnology / Q000379:methods; D044602:Cellulases / Q000235:genetics / Q000378:metabolism; D019662:Cucurbitaceae / Q000737:chemistry*; D055786:Gene Knockout Techniques; D006868:Hydrolysis; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism; D015394:Molecular Structure; D009154:Mutation; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000378:metabolism; D012503:Saponins / Q000737:chemistry / Q000378:metabolism; D014315:Triterpenes / Q000737:chemistry / Q000378:metabolism*
chemical_list: C081933:KRE6 protein, S cerevisiae; D008565:Membrane Proteins; D029701:Saccharomyces cerevisiae Proteins; D012503:Saponins; D014315:Triterpenes; C041740:mogroside V; D044602:Cellulases